Narrated 'Abdullah bin 'Ubaidullah bin Abi Mulaika: The sons of Suhaib, (Suhaib, who was the freed slave of Bani Jud'an) claimed that Allah's Messenger (ﷺ) had given two houses and one room to Suhaib. Marwan asked, "Who will testify to your claim?" They replied that Ibn 'Umar would do so. Marwan sent for Ibn 'Umar who testified that Allah's Messenger (ﷺ) had really given Suhaib two houses and a room. So, Marwan gave the verdict (in favour of Suhaib's sons), because of (Ibn 'Umar's) witness.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا إِبْرَاهِيمُ بْنُ مُوسَى، أَخْبَرَنَا هِشَامُ بْنُ يُوسُفَ، أَنَّ ابْنَ جُرَيْجٍ، أَخْبَرَهُمْ قَالَ أَخْبَرَنِي عَبْدُ اللَّهِ بْنُ عُبَيْدِ اللَّهِ بْنِ أَبِي مُلَيْكَةَ، أَنَّ بَنِي صُهَيْبٍ، مَوْلَى ابْنِ جُدْعَانَ ادَّعَوْا بَيْتَيْنِ وَحُجْرَةً، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم أَعْطَى ذَلِكَ صُهَيْبًا، فَقَالَ مَرْوَانُ مَنْ يَشْهَدُ لَكُمَا عَلَى ذَلِكَ قَالُوا ابْنُ عُمَرَ. فَدَعَاهُ فَشَهِدَ لأَعْطَى رَسُولُ اللَّهِ صلى الله عليه وسلم صُهَيْبًا بَيْتَيْنِ وَحُجْرَةً. فَقَضَى مَرْوَانُ بِشَهَادَتِهِ لَهُمْ.
sunnah.com